The inputs read-only property of the MIDIAccess interface provides access to any available MIDI input ports.

A MIDIInputMap instance.

The Navigator.requestMIDIAccess() method returns a promise that resolves with a MIDIAccess object. Printing the value of inputs to the console returns a MIDIInputMap.

navigator.requestMIDIAccess().then((access) => {
  console.log(access.inputs);
});